In the standoff between Greece and the rest of the eurozone over the fate of its bailout program, the European Central Bank’s latest move is equivalent to taking the safety catch off its gun. The question investors must consider is whether it could, or would, pull the trigger.

These securities were only eligible previously on the basis that Greece was in an agreed bailout program, as otherwise Greece’s junk credit rating would disqualify them.

The ECB, reasonably, has decided that the new Greek government’s repeated assertion that it doesn’t want an extension to its current bailout means that it is effectively no longer in a program. The central bank has, however, acted faster than might have been expected: Officially, Greece’s bailout runs until the end of February.

This means that the Greek banks will have to rely on emergency liquidity assistance from the Greek central bank, which can accept Greek government securities and offer funding, but at a higher rate and with bigger haircuts to the value of the collateral. That is fine as far as it goes: the Greek banks still have access to funding.

But the ECB can also restrict these emergency operations if they “interfere with the objectives and tasks of the Eurosystem.” The ECB has flexed its muscles like this before with Cyprus. There, it threatened to cut off assistance if a program wasn’t put in place that ensured the Cypriot banks were solvent. With Greece, the problem is more related to the amount of support that might end up being provided and whether it is against sufficiently good collateral.

It is highly questionable whether the ECB would take that decision on its own: Cutting off assistance would raise sharply the risk that Greece ends up leaving the euro. The exit of a eurozone member would undoubtedly “interfere with the objectives and tasks of the Eurosystem.” Perhaps assistance could be capped in some way. But that seems incompatible with the idea of emergency support for a banking system: if there are doubts about the provision of liquidity, it may hasten the onset of problems, like bank runs, that the support is designed to avoid.

Emergency liquidity assistance is supposed only to be a short-term solution. The simplest option for Greece involves accepting an extension of the bailout, buying time for a long-term deal to be thrashed out. That would require a U-turn from the Greek government.

But the longer that the current situation persists, the greater the risk is that the ECB has to consider whether it should be allowing emergency assistance to continue, with serious financial repercussions for Greece. That should be an incentive for Greece’s government to do some hard thinking.